Touch detection device, display device having touch detection function, electronic unit, and touch detection circuit

ABSTRACT

A touch detection device includes: a plurality of drive electrodes; a plurality of detection electrodes intersecting the plurality of drive electrodes, and each outputting, in response to driving of each of the drive electrodes, a series of detection signals; a signal correction section determining a reference based on the detection signals, and subtracting the determined reference from each of the detection signals; and a detecting section detecting an external proximity object based on corrected detection signals provided from the signal correction section.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a Continuation application of U.S. patentapplication Ser. No. 13/093,057 filed Apr. 25, 2011, which claimspriority to Japanese Priority Patent Application JP 2010-105575 filed inthe Japan Patent Office on Apr. 30, 2010, the entire content of which ishereby incorporated by reference.

BACKGROUND

The application relates to a touch detection device which detects anexternal proximity object such as a finger, to a display device having atouch detection function, to an electronic unit, and to a touchdetection circuit used for those devices.

In recent years, attention has been drawn to a display device in which acontact detection device, generally referred to as a touch panel, ismounted on a display such as a liquid crystal display, or in which thetouch panel and the display are integrated, and which allows the displayto display various button images etc. to thereby make it possible toinput information instead of providing typical mechanical buttons. Thedisplay device provided with the touch panel eliminates a necessity ofproviding an input device such as a keyboard, a mouse, and a keypad, andis thus being used more and more not only in a computer but also in aportable handheld terminal such as a cellular telephone.

There are a number of types of touch panels, including such as anoptical type and a resistance type. In devices such as the portablehandheld terminal, in particular, there are high expectations for atouch panel of an electrostatic capacitance type. The electrostaticcapacitance type touch panel has a relatively simple configuration, andis capable of reducing power consumption. However, the electrostaticcapacitance type touch panel is, in principle, susceptible to noiseattributed to an inverter fluorescent lamp, an AM (amplitude modulation)wave, an AC (alternating current) power source, or other noise source(hereinafter referred to as an “external noise”). In particular, adetection sensitivity is likely to be decreased in detecting a proximalstate or a “proximity” of an external proximity object, since asignal-to-noise (S/R) ratio deteriorates as compared with a case inwhich a contact state of the external proximity object is to bedetected.

Various studies have been made with a view toward providing a method forimproving a resistance to the external noise. For example, JapaneseUnexamined Patent Application Publication No. 2007-13432 (JP2007-13432A)discloses a touch panel in which electrostatic sensors, dedicated fordetecting the external noise, are provided around and providedseparately from an input electrostatic sensor used for detecting theproximity or the contact of the external proximity object. The disclosedtouch panel compares signals obtained from the noise-detectingelectrostatic sensors and the input electrostatic sensor to separate atouch component from an external noise component. A surface of thenoise-detecting electrostatic sensor is provided with a protectioncover, so that the noise-detecting electrostatic sensor makes noresponse to the external proximity object even when the externalproximity object is in contact thereto.

SUMMARY

However, the inventor/the inventors has/have found that, since an inputelectrostatic sensor and noise-detecting electrostatic sensors areprovided separately from one another in a fixed fashion in a touch paneldisclosed in JP2007-13432A, differences such as a difference inarrangement location of those electrostatic sensors, a difference insize of the electrostatic sensors, and a difference in a surroundingpart such as with or without a protection cover, cause an external noisecomponent inputted to the input electrostatic sensor and that inputtedto the noise-detecting electrostatic sensor to be different from oneanother. This makes a calculation, performed in obtaining a touchcomponent by subtracting the external noise component from the touchcomponent, to be complex, which in turn makes a configuration of a touchdetection circuit to be complex.

It is desirable to provide a touch detection device, a display devicehaving a touch detection function, an electronic unit, and a touchdetection circuit, capable of reducing an external noise component witha simple configuration.

A touch detection device according to an embodiment includes: aplurality of drive electrodes arranged side-by-side and extending in adirection; a plurality of detection electrodes arranged side-by-side,extending to intersect the drive electrodes, allowing an electrostaticcapacitance to be formed at each of intersections of the driveelectrodes and the detection electrodes, and each outputting a detectionsignal in response to driving of each of the drive electrodes; a signalcorrection section correcting the detection signals outputted from thedetection electrodes, through determining a reference based on thedetection signals, and through subtracting the determined reference fromeach of the detection signals; and a detecting section detecting anexternal proximity object based on corrected detection signals providedfrom the signal correction section.

A touch detection device according to another embodiment includes: aplurality of drive electrodes; a plurality of detection electrodesintersecting the plurality of drive electrodes, and each outputting, inresponse to driving of each of the drive electrodes, a series ofdetection signals; a signal correction section determining a referencebased on the detection signals, and subtracting the determined referencefrom each of the detection signals; and a detecting section detecting anexternal proximity object based on corrected detection signals providedfrom the signal correction section.

A display device having a touch detection function according to anembodiment includes: a display section performing display based on animage signal; a plurality of drive electrodes arranged side-by-side andextending in a direction; a plurality of detection electrodes arrangedside-by-side, extending to intersect the drive electrodes, allowing anelectrostatic capacitance to be formed at each of intersections of thedrive electrodes and the detection electrodes, and each outputting adetection signal in response to driving of each of the drive electrodes;a signal correction section correcting the detection signals outputtedfrom the detection electrodes, through determining a reference based onthe detection signals, and through subtracting the determined referencefrom each of the detection signals; and a detecting section detecting anexternal proximity object based on corrected detection signals providedfrom the signal correction section.

An electronic unit according to an embodiment includes: a touchdetection device; and a control section performing an operation controlthat utilizes the touch detection device. The touch detection deviceincludes: a plurality of drive electrodes arranged side-by-side andextending in a direction; a plurality of detection electrodes arrangedside-by-side, extending to intersect the drive electrodes, allowing anelectrostatic capacitance to be formed at each of intersections of thedrive electrodes and the detection electrodes, and each outputting adetection signal in response to driving of each of the drive electrodes;a signal correction section correcting the detection signals outputtedfrom the detection electrodes, through determining a reference based onthe detection signals, and through subtracting the determined referencefrom each of the detection signals; and a detecting section detecting anexternal proximity object based on corrected detection signals providedfrom the signal correction section. As used herein, the term “electronicunit” refers to any devices in which a detection of a touch or aproximity of the external proximity object is desirable. The electronicunit includes, such as but not limited to, a television device, adigital camera, a computer including a desk-top personal computer and alaptop personal computer, a portable terminal device including acellular phone, and a video camera.

A touch detection circuit according to an embodiment includes: a signalcorrection section correcting detection signals through determining areference based on the detection signals and through subtracting thedetermined reference from each of the detection signals, the detectionsignals being outputted from detection electrodes, the detectionelectrodes being arranged side-by-side, extending to intersect driveelectrodes arranged side-by-side and extending in a direction, allowingan electrostatic capacitance to be formed at each of intersections ofthe drive electrodes and the detection electrodes, and each outputtingthe detection signal in response to driving of each of the driveelectrodes; and a detecting section detecting an external proximityobject based on corrected detection signals provided from the signalcorrection section.

In the touch detection devices, the display device having the touchdetection function, the electronic unit, and the touch detection circuitaccording to the embodiments, the detection signals corresponding to aproximity or a touch of the external proximity object are supplied tothe signal correction section. Each of the detection signals includes atouch component in which amplitude becomes large in accordance with theproximity or the touch of the external proximity object. The detectionsignal may include a noise component in addition to the touch component.The signal correction section determines, based on the detectionsignals, the reference that hardly includes the touch component, andsubtracts the reference from each of the detection signals, to therebyextract the touch component.

Advantageously, the signal correction section calculates, for each ofthe detection electrodes, a time-average of absolute value of a sum of atouch component and a noise component both contained in the detectionsignal outputted from the corresponding detection electrode, selects asmallest time-average from the plurality of time-averages obtained, anduses, as the reference, a time-average of a detection signal which hasbrought the selected smallest time-average. Alternatively, the signalcorrection section calculates, for each of the detection electrodes, atime-average of a variation component in the detection signal outputtedfrom the corresponding detection electrode, selects a smallesttime-average from the plurality of time-averages obtained, and uses, asthe reference, a time-average of a detection signal which has broughtthe selected smallest time-average.

Advantageously, the signal correction section determines, for each ofthe detection electrodes, a minimum of absolute value of a sum of atouch component and a noise component both contained in the detectionsignal outputted from the corresponding detection electrode, selects asmallest minimum from the plurality of minimums obtained, and uses, asthe reference, a detection signal which has brought the smallestminimum. Alternatively, the signal correction section determines, foreach of the detection electrodes, a minimum of absolute value of avariation component in the detection signal outputted from thecorresponding detection electrode, selects a smallest minimum from theplurality of minimums obtained, and uses, as the reference, a detectionsignal which has brought the smallest minimum.

Advantageously, the signal correction section subtracts the currentreference from each of the current detection signals. The currentreference is determined from the current detection frame, and thecurrent detection signals are obtained from the respective detectionelectrodes in the current detection frame.

Advantageously, the signal correction section temporarily holds thecurrent detection signals obtained from the respective the detectionelectrodes.

Advantageously, the signal correction section subtracts the precedingreference from each of the current detection signals. The precedingreference is determined from the preceding detection frame, and thecurrent detection signals are obtained from the respective detectionelectrodes in the current detection frame.

According to the touch detection devices, the display device having thetouch detection function, the electronic unit, and the touch detectioncircuit of the embodiments, the reference is determined based on thedetection signals, and the reference is subtracted from each of thedetection signals. Therefore, it is possible to reduce the externalnoise component with a simple configuration.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the technology as claimed.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments and,together with the specification, serve to explain the principles of thetechnology.

FIG. 1 is an explanatory diagram for describing a basic principle of atouch detection scheme in a display device having a touch detectionfunction according to embodiments of the application, and illustrates acase where an external proximity object such as a finger is not in acontact state nor is in a proximity state.

FIG. 2 is an explanatory diagram for describing the basic principle ofthe touch detection scheme in the display device having the touchdetection function according to the embodiments, and illustrates a casewhere the finger is in the contact state or is in the proximity state.

FIG. 3 is an explanatory diagram for describing the basic principle ofthe touch detection scheme in the display device having the touchdetection function according to the embodiments, and illustrates anexample of a waveform of a drive signal and an example of a waveform ofa touch detection signal.

FIG. 4 is a block diagram illustrating a configuration example of adisplay device having a touch detection function according to a firstembodiment.

FIG. 5 is a cross-sectional view illustrating a schematiccross-sectional configuration of a touch detection function display unitillustrated in FIG. 4.

FIG. 6 is a circuit diagram illustrating a pixel array of the touchdetection function display unit illustrated in FIG. 4.

FIG. 7 is a perspective view illustrating a configuration example of adrive electrode and that of a touch detection electrode of the touchdetection function display unit illustrated in FIG. 4.

FIG. 8 is a circuit diagram illustrating a configuration example of atouch detection circuit illustrated in FIG. 4.

FIG. 9 is a timing waveform diagram illustrating an example of anoperation of the display device having the touch detection functionillustrated in FIG. 4.

FIG. 10 is a flowchart illustrating an example of an operation of thetouch detection circuit illustrated in FIG. 4.

FIGS. 11A and 11B each schematically illustrate an example of anoperation of a reference touch detection electrode of the touchdetection function display unit illustrated in FIG. 4.

FIG. 12 is a circuit diagram illustrating a configuration example of atouch detection circuit according to a first modification of the firstembodiment.

FIG. 13 is a circuit diagram illustrating a configuration example of atouch detection circuit according to a second modification of the firstembodiment.

FIG. 14 is a circuit diagram illustrating a configuration example of atouch detection circuit according to a second embodiment.

FIG. 15 is a flowchart illustrating an example of an operation of thetouch detection circuit illustrated in FIG. 14.

FIG. 16 is a perspective view illustrating an external configuration ofa first application example to which the display device having the touchdetection function according to any one of the embodiments and themodifications is applied.

FIGS. 17A and 17B are perspective views each illustrating an externalconfiguration of a second application example.

FIG. 18 is a perspective view illustrating an external configuration ofa third application example.

FIG. 19 is a perspective view illustrating an external configuration ofa fourth application example.

FIG. 20A is a front view in an open state, FIG. 20B is a side view inthe open state, FIG. 20C is a front view in a closed state, FIG. 20D isa left side view, FIG. 20E is a right side view, FIG. 20F is a top view,and FIG. 20G is a bottom view, each illustrating an externalconfiguration of a fifth application example.

FIG. 21 is a cross-sectional view illustrating a schematiccross-sectional configuration of a touch detection function display unitaccording to a modification of each of the embodiments and themodifications.

DETAILED DESCRIPTION

Embodiments of the present application will be described below in detailwith reference to the drawings.

1. Basic Principle of Electrostatic Capacitance Type Touch Detection

2. First Embodiment

3. Second Embodiment

4. Application Examples

1. BASIC PRINCIPLE OF ELECTROSTATIC CAPACITANCE TYPE TOUCH DETECTION

First, with reference to FIGS. 1 to 3, a basic principle of a touchdetection in a display device having a touch detection functionaccording to embodiments will be described. This touch detection schemeis embodied as an electrostatic capacitance type touch sensor. Forexample, as illustrated in (A) of FIG. 1, a pair of electrodes (a driveelectrode E1 and a touch detection electrode E2), which are disposed toface each other with a dielectric D interposed in between, are used toconfigure a capacitor element C1. This configuration is representable asan equivalent circuit illustrated in (B) of FIG. 1. The capacitorelement C1 is configured by the drive electrode E1, the detectionelectrode E2, and the dielectric D. The capacitor element C1 has a firstend connected to an AC signal source (a drive signal source) S, and asecond end P grounded through a resistor R and connected to a voltagedetector (a touch detection circuit) DET. When an AC rectangular wave Sg((B) of FIG. 3) having a predetermined frequency (for example,approximately several kHz to ten-odd kHz) is applied from the AC signalsource S to the drive electrode E1 (the first end of the capacitorelement C1), an output waveform (a touch detection signal Vdet)illustrated in (A) of FIG. 3 appears in the detection electrode E2 (thesecond end P of the capacitor element C1). This AC rectangular wave Sgis equivalent to a drive signal Vcom, which will be described later.

As illustrated in FIG. 1, in a case where an external proximity object(such as a finger in the exemplary embodiments, although a member suchas a pen may be used) is not in a contact state nor is in a proximitystate, a current I0 corresponding to a capacitance value of thecapacitor element C1 flows in accordance with charge/discharge performedon the capacitor element C1. An electric potential waveform of thesecond end P in the capacitor element C1 at this time is, for example,as illustrated by a waveform V0 in (A) of FIG. 3, which is detected bythe voltage detector DET.

On the other hand, in a case where the finger is in the contact state oris in the proximity state, a capacitor element C2 formed by the fingeris added in series to the capacitor element C1, as illustrated in FIG.2. In this state, when charge/discharge is performed on the capacitorelements C1 and C2, currents I1 and I2 flow, respectively. The electricpotential waveform of the second end P in the capacitor element C1 atthis time is, for example, as illustrated by a waveform V1 in (A) ofFIG. 3, which is detected by the voltage detector DET. Herein, anelectric potential at the second end P is a divided electric potentialdetermined by values of the currents I1 and I2 flowing through thecapacitor elements C1 and C2, respectively. Hence, the waveform V1 issmaller in value than the waveform V0 derived from the non-contact stateor from the non-proximity state. The voltage detector DET compares thedetected voltage with a predetermined threshold voltage Vth. The voltagedetector DET determines that the finger is in the non-contact state oris in the non-proximity state when the detected voltage is equal to orlarger than the threshold voltage Vth, whereas, the detector DETdetermines that the finger is in the contact state or is in theproximity state when the detected voltage is smaller than the thresholdvoltage Vth, thereby making it possible to perform the touch detection.

2. FIRST EMBODIMENT Configuration Example Overall Configuration

FIG. 4 illustrates a configuration example of a display device having atouch detection function according to a first embodiment. It is to benoted that this embodiment is applicable to and embodies a touchdetection device and a touch detection circuit according to embodimentsof the application as well. Hence, description on the touch detectiondevice and the touch detection circuit will be given collectively inconjunction with this embodiment. The display device having the touchdetection function according to this embodiment is a device of aso-called “in-cell” type, in which a liquid crystal display element isused as a display element, and in which a liquid crystal display unit,configured by the liquid crystal display element, and a touch detectionunit of an electrostatic capacitance type are integrated.

The display device having the touch detection function 1 is providedwith a control section 11, a gate driver 12, a source driver 13, a driveelectrode driver 14, a display unit having a touch detection function(hereinafter simply referred to as a “touch detection function displayunit”) 10, and a touch detection circuit 40.

The control section 11 supplies, based on a picture signal Vdispsupplied from the outside, a control signal to each of the gate driver12, the source driver 13, the drive electrode driver 14, and the touchdetection circuit 40, and controls the gate driver 12, the source driver13, the drive electrode driver 14, and the touch detection circuit 40 sothat they operate in a mutually-synchronized fashion.

The gate driver 12 serves to sequentially select, based on the controlsignal supplied from the control section 11, a display horizontal line(one display horizontal line) subjected to a display drive performed bythe touch detection function display unit 10. As will be described laterin greater detail, the gate driver 12 applies a scan signal Vscanthrough a scan signal line GCL to a gate of a TFT (thin-film transistor)element Tr in a pixel Pix. Thereby, the gate driver 12 sequentiallyselects a row (i.e., one display horizontal line) among the pixels Pix,which are formed in matrix in a liquid crystal display unit 20 of thetouch detection function display unit 10, as the row of the pixels Pixsubjected to the display drive.

The source driver 13 supplies, based on the control signal supplied fromthe control section 11, a pixel signal Vpix to each of thelater-described pixels Pix in the touch detection function display unit10. As will be described later in greater detail, the source driver 13supplies the pixel signal Vpix through a pixel signal line SGL to eachof the pixels Pix structuring one display horizontal line which issequentially selected by the gate driver 12. Those pixels Pix that aresupplied with the pixel signals Vpix perform, in accordance with thesupplied pixels signals Vpix, display of the one display horizontalline.

The drive electrode driver 14 supplies, based on the control signalsupplied from the control section 11, the drive signals Vcom tolater-described drive electrodes COML in the touch detection functiondisplay unit 10. The drive electrode driver 14 applies display drivesignals, serving as the drive signals Vcom, to all of the driveelectrodes COML in the touch detection function display unit 10 during aperiod in which the touch detection function display unit 10 performsthe display (i.e., a display period). On the other hand, during a periodof performing the touch detection (i.e., a touch detection period), thedrive electrode driver 14 sequentially applies pulsed touch drivesignals, serving as the drive signals Vcom, to the drive electrodes COMLin the touch detection function display unit 10, to thereby sequentiallyselect a detection horizontal line (one detection horizontal line)subjected to the touch detection performed by a touch detection unit 30.The touch detection unit 30 then outputs, per one detection horizontalline, the touch detection signals Vdet from a later-described pluralityof touch detection electrodes TDL, and supplies those touch detectionsignals Vdet to the touch detection circuit 40. In the display periodaccording to this embodiment, the drive signal Vcom (the display drivesignal) is a direct current signal having a voltage of zero volts, andthe pixels signals Vpix in the mutually-adjacent pixels Pix are reversedin polarity from each other. In other words, in this embodiment, theliquid crystal display unit 20 is driven based on a so-calleddot-inversion driving scheme.

The touch detection function display unit 10 is a display unit whichincludes the touch detection function therein. The touch detectionfunction display unit 10 is provided with the liquid crystal displayunit 20 and the touch detection unit 30. The liquid crystal display unit20 sequentially scans, in accordance with a gate signal supplied fromthe gate driver 12, one display horizontal line at a time to perform thedisplay, as will be described later. The touch detection unit 30operates based on the basic principle of the electrostatic capacitancetype touch detection described above, and outputs the touch detectionsignals Vdet. The touch detection unit 30 sequentially scans, inaccordance with the drive electrode driver 14, one detection horizontalline at a time to perform the touch detection.

The touch detection circuit 40 detects a presence of touch or proximitywith respect to the touch detection unit 30, based on the control signalsupplied from the control section 11 and on the touch detection signalsVdet supplied from the touch detection unit 30 of the touch detectionfunction display unit 10. The touch detection circuit 40, when there isthe presence of touch or proximity, obtains a coordinate of the detectedtouch or the detected proximity in a touch detection region.

Touch Detection Function Display Unit 10

A configuration example of the touch detection function display unit 10will now be described in more detail.

FIG. 5 illustrates an example of a schematic cross-sectionalconfiguration of the touch detection function display unit 10. The touchdetection function display unit 10 includes a pixel substrate 2, anopposed substrate 3 disposed to face the pixel substrate 2, and a liquidcrystal layer 6 inserted between the pixel substrate 2 and the opposedsubstrate 3.

The pixel substrate 2 includes a TFT substrate 21 serving as a circuitsubstrate, and a plurality of pixel electrodes 22 disposed in matrix onthe TFT substrate 21. The TFT substrate 21 is formed with TFTs for therespective pixels, and wirings such as the pixels signal lines SGL forsupplying the image signals Vpix to the respective pixel electrodes 22and the scan signal lines GCL for driving the respective TFTs, which arenot illustrated in FIG. 5.

The opposed substrate 3 includes a glass substrate 31, a color filter 32formed on a first surface of the glass substrate 31, and the pluralityof drive electrodes COML formed on the color filter 42. The color filter42 has a configuration in which, for example, color filter layers ofthree colors of red (R), green (G), and blue (B) are periodicallyaligned. Herein, a set of three colors of R, G and B is assigned to eachdisplay pixel, although the number of colors and the types of colors arenot limited thereto. The drive electrode COML serves as a common driveelectrode of the liquid crystal display unit 20, and also serves as adrive electrode of the touch detection unit 30. The drive electrode COMLis coupled to the TFT substrate 21 by an unillustrated contactconductive pillar 7. The drive signal Vcom having an AC rectangularwaveform is applied from the TFT substrate 21 through the contactconductive pillar 7 to the drive electrode COML. As illustrated in FIG.5, each of the drive electrodes COML is provided to correspond to twopixels electrodes 22, although it is not limited thereto. In oneembodiment, the drive electrode COML may be arranged to correspond toone pixel electrode 22, or may be arranged to correspond to three ormore pixel electrodes 22. A second surface of the glass substrate 31 isformed with the touch detection electrodes TDL serving as detectionelectrodes of the touch detection unit 30, on which touch detectionelectrodes TDL a polarizing plate 35 is disposed.

The liquid crystal layer 6 modulates light passing therethrough inresponse to a state of an electric field, and is configured of a liquidcrystal in any of various modes such as a TN (Twisted Nematic) mode, aVA (Vertical Alignment) mode, and an ECB (Electrically-ControlledBirefringence) mode.

Alignment films are respectively disposed between the liquid crystallayer 6 and the pixel substrate 2 and between the liquid crystal layer 6and the opposed substrate 3, and a light-incident side polarizing plateis disposed below the pixel substrate 2, illustrations of which areomitted in the drawings.

FIG. 6 illustrates an example of a pixel configuration in the liquidcrystal display unit 20. The liquid crystal display unit 20 includes theplurality of pixels Pix which are arranged in matrix. The pixel Pixincludes the TFT element Tr and a liquid crystal element LC. The TFTelement Tr is configured by a thin-film transistor, and in thisembodiment is configured by a TFT of an n-channel metal-oxidesemiconductor (MOS), although it is not limited thereto. The TFT elementTr has a source connected to the pixel signal line SGL, the gateconnected to the scan signal line GCL, and a drain connected to a firstend of the liquid crystal element LC. The liquid crystal element LC hasthe first end connected to the drain of the TFT element TR, and a secondend connected to the drive electrode COML.

The pixel Pix is connected mutually, through the scan signal line GCL,to other pixels Pix that belong to the same row in the liquid crystaldisplay unit 20. The scan signal line GCL is connected to the gatedriver 12, and is supplied with the scan signal Vscan by the gate driver12. The pixel Pix is connected mutually, through the pixel signal lineSGL, to other pixels Pix that belong to the same column in the liquidcrystal display unit 20. The pixel signal line SGL is connected to thesource driver 13, and is supplied with the pixel signal Vpix by thesource driver 13.

The pixel Pix is further connected mutually, through the drive electrodeCOML, to other pixels Pix that belong to the same row in the liquidcrystal display unit 20. The drive electrode COML is connected to thedrive electrode driver 14, and is supplied with the drive signal Vcom bythe drive electrode driver 14. In other words, in this embodiment, theplurality of pixels Pix that belong to the same one row share one driveelectrode COML. In an alternative embodiment, the plurality of pixelsPix belonging to the plurality of rows (two rows in FIG. 2, although itis not limited thereto) may share one drive electrode COML.

With this configuration, in the liquid crystal display unit 20, the gatedriver 12 so drives the scan signal lines GCL as to performline-sequential scanning of the scan signal lines GCL in atime-divisional fashion to thereby allow one display horizontal line tobe selected sequentially, and the source driver 13 supplies the pixelsignals Vpix to the pixels Pix which belong to that one displayhorizontal line, thus allowing the display to be performed one displayhorizontal line at a time. In performing this display operation, thedrive electrode driver 14 applies a common voltage (zero volts in thisembodiment) to all of the drive electrodes COML.

FIG. 7 is a perspective view illustrating a configuration example of thetouch detection unit 30. The touch detection unit 30 is configured bythe drive electrodes COML and the touch detection electrodes TDL, bothof which are provided in the opposed substrate 3. The drive electrodesCOML configure a plurality of stripe-shaped electrode patternsextending, for example, in a horizontal direction in the figure. In thetouch detection period, the respective electrode patterns aresequentially supplied with the drive signals Vcom by the drive electrodedriver 14, and are driven with the line-sequential scanning in atime-divisional fashion as will be described later in detail. The touchdetection electrodes TDL configure k-number of stripe-shaped electrodepatterns (“k” is a natural number) extending in a direction orthogonalto the extending direction of the drive electrodes COML. Each of theelectrode patterns of the touch detection electrodes TDL is connected toan input of the touch detection circuit 40. The electrode patterns whichintersect one another by the drive electrode COML and the touchdetection electrode TDL form an electrostatic capacitance at a locationat which the drive electrode COML and the touch detection electrode TDLintersect each other.

With this configuration, in the touch detection period, the driveelectrode driver 14 so drives the drive electrodes COML as to performline-sequential scanning of the drive electrodes COML in atime-divisional fashion to thereby allow one detection horizontal lineto be selected sequentially, and the touch detection signals Vdet areoutputted from the touch detection electrodes TDL, thus allowing thetouch detection for the one detection horizontal line to be performed,in the touch detection unit 30. In other words, the drive electrode COMLcorresponds to the drive electrode E1 and the touch detection electrodeTDL corresponds to the touch detection electrode E2 in the basicprinciple of the touch detection described above with reference to FIGS.1 to 3, and the touch detection unit 30 detects the touch or theproximity in accordance with the basic principle. Hence, the touchdetection signal Vdet is higher in voltage when there is no touch orproximity, and is lower in voltage when there is touch or proximity. Asillustrated in FIG. 7, the electrode patterns, which intersect oneanother, configure the electrostatic capacitance type touch sensor in amatrix form. Thus, the scanning throughout the entire touch detectionplane of the touch detection unit 30 makes it possible to detect aposition at which the contact or the proximity of the external proximityobject has occurred.

Touch Detection Circuit 40

A configuration example of the touch detection circuit 40 will now bedescribed in detail.

FIG. 8 illustrates an example of a circuit configuration of the touchdetection circuit 40. The touch detection circuit 40 is provided with aLPF (Low Pass Filter) section 41, an ADC (Analog-to-Digital Converter)section 42, a digital LPF section 43, an average value calculatingsection 44, a maximum value selecting circuit 45, a memory 46, asubtracting section 47, a binarizing circuit 48, and a coordinateextracting circuit 49.

The LPF section 41 serves as a low-pass analog filter which removes ahigh-frequency component from each of the touch detection signals Vdetsupplied from the k-number of touch detection electrodes TDL, andoutputs the touch detection signals Vdet subjected to the high-frequencycomponent removal. In one embodiment, the LPF section 41 may have afunction of amplifying the signal inputted thereto. Further, registersR1 to Rk for applying a DC potential (e.g., zero volts) are eachconnected or inserted between an input terminal and the ground. In oneembodiment, switches may be provided instead of the resistors R1 to Rk,and the switches may be turned ON during a predetermined time to applythe DC potential (e.g., zero volts). The ADC section 42 is a circuitwhich converts the analog signals supplied from the LPF section 41 intodigital signals. The digital LPF section 43 utilizes time-series data ofthe digital signals supplied respectively from the ADC section 42 toperform computing of a low-pass filter, and outputs thus-obtainedresults as touch detection data DT.

The average value calculating section 44 is an arithmetic circuit whichcomputes an average value, in a time period it takes to perform thescanning of the touch detection throughout the entire touch detectionplane (i.e., one detection frame period TF), of each of the touchdetection data DT supplied from the digital LPF section 43, and outputsthus-obtained average values as average data DAVG. The maximum valueselecting circuit 45 is an arithmetic circuit which selects, for eachone detection frame, the maximum one of the average data DAVG suppliedrespectively from the average value calculating section 44, and outputsthe selected maximum average data DAVG as reference data DR. The memory46 holds and accumulates therein the touch detection data DT, of the onedetection frame, that are supplied respectively from the digital LPFsection 43.

The subtracting section 47 is an arithmetic circuit which subtracts thereference data DR, supplied from the maximum value selecting circuit 45,from each of the touch detection data DT supplied from the memory 46.The binarizing circuit 48 is an arithmetic circuit which compares eachdata supplied from the subtracting section 47 with a predeterminedthreshold value to perform binarization. The coordinate extractingcircuit 49 extracts, based on data supplied from the binarizing circuit48, the coordinate at which the touch or the proximity is made oroccurred in the touch detection plane of the touch detection unit 30.

In this embodiment, the LPF section 41, the ADC section 42, the digitalLPF section 43, the average value calculating section 44, and thesubtracting section 47 each perform parallel processing of the pluralityof touch detection signals Vdet, although it is not limited thereto. Inan alternative embodiment, a part of or all of those sections mayperform serial processing of signals such as the time-divisionmultiplexed touch detection signals Vdet, for example.

With the configuration described in the foregoing, the average valuecalculating section 44 and the maximum value selecting circuit 45extracts, when the touch detection signals Vdet containing a touchcomponent and an external noise component are supplied to the touchdetection circuit 40, the external noise component (the reference dataDR), and the subtracting section 47 subtracts the extracted externalnoise component from the touch detection data DT, to thereby obtain thetouch component, in the touch detection circuit 40. This will bedescribed later in greater detail.

In one embodiment, the touch detection electrode TDL is a specificexample of a “detection electrode”. The touch detection signal Vdet is aspecific example of a “detection signal”. The reference data DR is aspecific example of a “reference”. The LPF section 41, the ADC section42, the digital LPF section 43, the average value calculating section44, the maximum value selecting circuit 45, the memory 46, and thesubtracting section 47 are a specific example of a “signal correctionsection”. The binarizing circuit 48 and the coordinate extractingcircuit 49 are a specific example of a “detecting section”.

Operation and Function

An operation and a function of the display device having the touchdetection function 1 will now be described.

Outline of Overall Operation

The control section 11 supplies, based on the picture signal Vdispsupplied from the outside, the control signal to each of the gate driver12, the source driver 13, the drive electrode driver 14, and the touchdetection circuit 40, and controls the gate driver 12, the source driver13, the drive electrode driver 14, and the touch detection circuit 40 sothat they operate in a mutually-synchronized fashion. The gate driver 12supplies, based on the control signal supplied from the control section11, the scan signals Vscan to the liquid crystal display unit 20, tosequentially select one display horizontal line subjected to the displaydrive. The source driver 13 supplies, based on the control signalsupplied from the control section 11, the pixel signal Vpix to each ofthe pixels Pix structuring the one display horizontal line selected bythe gate driver 12. The drive electrode driver 14, based on the controlsignal supplied from the control section 11, applies the display drivesignals (e.g., the DC signal of zero volts) serving as the drive signalsVcom to all of the drive electrodes COML during the display period,whereas the drive electrode driver 14 sequentially applies the pulsedtouch drive signals serving as the drive signals Vcom to the driveelectrodes COML to thereby sequentially select one detection horizontalline during the touch detection period. The touch detection functiondisplay unit 10 performs the display operation based on the signalssupplied from the gate driver 12, the source driver 13, and the driveelectrode driver 14 during the display period, and performs, during thetouch detection period, the touch detection operation based on thesignals supplied from the drive electrode driver 14, and outputs thetouch detection signals Vdet from the touch detection electrodes TDL.

In the touch detection circuit 40, the LPF section 41 performs thehigh-frequency component removal on the touch detection signals Vdetsupplied from the touch detection function display unit 10, and outputsthe touch detection signals Vdet subjected to the high-frequencycomponent removal. The ADC section 42 converts the analog signalssupplied from the LPF section 41 into the digital signals. The digitalLPF section 43 utilizes the time-series data of the digital signalssupplied from the ADC section 42 to perform the computing of thelow-pass filter, and outputs the thus-obtained results as the touchdetection data DT. The average value calculating section 44 computes theaverage value in one detection frame period TF of each of the touchdetection data DT supplied from the digital LPF section 43. The maximumvalue selecting circuit 45 selects, for each one detection frame, themaximum one of the data supplied respectively from the average valuecalculating section 44, and outputs the selected maximum average dataDAVG as the reference data DR. The memory 46 accumulates therein thetouch detection data DT for the one detection frame that are suppliedfrom the digital LPF section 43. The subtracting section 47 subtractsthe reference data DR from each of the touch detection data DT suppliedfrom the memory 46. The binarizing circuit 48 compares each of the datasupplied from the subtracting section 47 with the predeterminedthreshold value to perform the binarization. The coordinate extractingcircuit 49 extracts, based on the data supplied from the binarizingcircuit 48, the coordinate at which the touch or the proximity is madeor occurred.

Example of Detailed Operation of Touch Detection Function Display Unit10

FIG. 9 illustrates an example of a detailed operation of the displaydevice having the touch detection function 1. In FIG. 9, (A) illustrateswaveforms of the scan signals Vscan, (B) illustrates waveforms of thedrive signals Vcom, (C) illustrates a waveform of the pixel signal Vpix,and (D) illustrates a waveform of the touch detection signal Vdet.Herein, the scan signals Vscan illustrated in (A) of FIG. 9 are thosebelonging to the (n−1)th row, n-th row, and (n+1)th row, which areadjacent to one another, of the scan signal lines GCL, respectively.Similarly, the drive signals Vcom illustrated in (B) of FIG. 9 are thosebelonging to the (m−1)th row, m-th row, and (m+1)th row, which areadjacent to one another, of the common electrodes COML, respectively.

The display device having the touch detection function 1time-divisionally performs the touch detection operation (a touchdetection period A) and the display operation (a display period B) foreach one display horizontal period (1H). In the touch detectionoperation, the display device having the touch detection function 1selects, for each one display horizontal period (1H), different driveelectrode COML and applies the drive signal Vcom thereto to perform thescanning of the touch detection. In the following, description is givenon those operations in detail.

First, the gate driver 12 applies the scan signal Vscan to the scansignal line GCL in the (N−1)th row, by which a scan signal Vscan(n−1)changes from a low level to a high level ((A) of FIG. 9). This startsone display horizontal period (1H).

Then, in the touch detection period A, the drive electrode driver 14applies the drive signal Vcom to the drive electrode COML in the (m−1)throw, by which a drive signal Vcom(m−1) changes from a low level to ahigh level ((B) of FIG. 9). This drive signal Vcom(m−1) is transmittedto the touch detection electrode TDL through an electrostaticcapacitance, allowing the touch detection signal Vdet to be changed ((D)of FIG. 9). Then, when the drive signal Vcom(m−1) changes from the highlevel to the low level ((B) of FIG. 9), the touch detection signal Vdetchanges likewise ((D) of FIG. 9). The waveform of the touch detectionsignal Vdet in this touch detection period A corresponds to that of thetouch detection signal Vdet ((A) of FIG. 3) in the basic principle ofthe touch detection described above. In other words, the touch detectionsignal Vdet is high in voltage when there is no touch or proximity, andis low in voltage when there is touch or proximity. The ADC section 42performs an analog-to-digital conversion on the touch detection signalVdet in this touch detection period A to perform the touch detection.Thereby, the touch detection for one detection horizontal line isperformed in the display device having the touch detection function 1.

Next, in the display period B, the source driver 13 applies the pixelsignal Vpix to the pixel signal line SGL ((C) of FIG. 9) to perform thedisplay for one display horizontal line. It is to be noted that, asillustrated in (D) of FIG. 9, this change in the pixel signal Vpix maybe transmitted to the touch detection electrode TDL through theelectrostatic capacitance, and may in turn change the touch detectionsignal Vdet. However, in the display period B, the ADC section 42 may beadapted not to perform the analog-to-digital conversion, to therebysuppress an influence of the change of the pixel signal Vpix on thetouch detection. When the supplying of the pixel signal Vpix by thesource driver 13 has completed, the gate driver 12 then changes the scansignal Vscan(n−1) belonging to the scan signal line GCL in the (n−1)throw from the high level to the low level ((A) of FIG. 9). This ends theone display horizontal period.

Next, the gate driver 12 applies the scan signal Vscan to the scansignal line GCL in the n-th row which is different one from the previousscan signal line GCL, by which a scan signal Vscan(n) changes from a lowlevel to a high level ((A) of FIG. 9). This starts the subsequent onedisplay horizontal period (1H).

Then, in the touch detection period A, the drive electrode driver 14applies the drive signal Vcom to the drive electrode COML in the (m)throw which is different one from the previous drive electrode COML ((B)of FIG. 9). A change in the touch detection signal Vdet accompaniedthereby ((D) of FIG. 9) is subjected to the analog-to-digital conversionby the ADC section 42. Thereby, the touch detection for this onedetection horizontal line is performed.

Next, in the display period B, the source driver 13 applies the pixelsignal Vpix to the pixel signal line SGL ((C) of FIG. 9) to perform thedisplay for one display horizontal line. It is to be noted that, in thisembodiment, the display device having the touch detection function 1performs the dot-inversion drive. Hence, the pixel signal Vpix appliedby the source driver 13 is reversed in polarity as compared with thatapplied in the preceding one display horizontal period. The completionof this display period B ends the present one display horizontal period.

From then on, the display device having the touch detection function 1repeats the operation described before, to thereby perform the displayoperation by the scanning throughout the entire display plane, and thetouch detection operation by the scanning throughout the entire touchdetection plane.

Example of Detailed Operation of Touch Detection Circuit 40

An operation of the touch detection circuit 40 will now be described.Herein, on the assumption that there is an external noise, descriptionis given based on an example where the touch detection function displayunit 10 outputs from the touch detection electrode TDL the touchdetection signal Vdet that contains the touch component and the externalnoise component. In this description, the external noise component issubstantially constant irrespective of the touch detection electrodesTDL as can be typically considered.

FIG. 10 is a flowchart of the operation of the touch detection circuit40. The touch detection circuit 40, when the touch detection signalsVdet each containing the touch component and the external noisecomponent are inputted therein, accumulates the touch detection data DTof the one detection frame that correspond to those touch detectionsignals Vdet into the memory 46, and extracts, as the reference data DR,the external noise component from the touch detection data DT. Then, thetouch detection circuit 40 subtracts the reference data DR from each ofthe touch detection data DT accumulated in the memory 46 to extract thetouch component, and obtains, based on the extracted touch component,the coordinate at which the touch or the proximity is made or occurredin the touch detection plane. In the following, description is given oneach step.

First, the touch detection circuit 40 accumulates the touch detectiondata DT in accordance with the scanning of the one detection frame, andcalculates the average value of the touch detection data DT for each ofthe touch detection electrodes TDL (Step S1). More specifically, the LPFsection 41, the ADC section 42, and the digital LPF section 43 generate,based on the touch detection signals Vdet inputted from the touchdetection electrodes TDL, the touch detection data DT. Then, the memory46 holds and accumulates therein the touch detection data DT for the onedetection frame. At the same time, the average value calculating section44 calculates the average value of the touch detection data DT in onedetection frame period TF of each of the touch detection electrodes TDL,and outputs the respective thus-calculated average values as the averagedata DAVG. The touch detection signal Vdet belonging to the touchdetection electrode TDL in which the touch is made or the proximity isoccurred contains a large amount of touch component, and thus theaverage value of the touch detection data (the average data DAVG)becomes low in value. On the other hand, the touch detection signal Vdetbelonging to the touch detection electrode TDL to which no touch is madeor no proximity is occurred contains no touch component, and thus theaverage data DAVG becomes high in value. In other words, the averagedata DAVG derived from the touch detection electrode TDL in which notouch is made or no proximity is occurred corresponds to the externalnoise component.

Then, the maximum value selecting circuit 45 selects the average dataDAVG that has the maximum value among the average data DAVG of therespective touch detection electrodes TDL obtained by the average valuecalculating section 44 as the reference data DR (Step S2). This isequivalent to the selection of the previously-described average dataDAVG that is derived from the touch detection electrode TDL in which notouch is made or no proximity is occurred. In other words, the maximumvalue selecting circuit 45 selects the average data DAVG in which amagnitude (or an absolute value) of a sum of the touch component and thenoise component is the smallest. That is, a time-average of the absolutevalue of the sum of the touch component and the noise component, bothcontained in the detection signal outputted from the correspondingdetection electrode, is calculated for each of the detection electrodes,a smallest time-average is selected from the plurality of time-averagesobtained, and a time-average of a detection signal which has brought theselected smallest time-average is used as the reference. Thereby, thereference data DR corresponds to the external noise component.

In the following, the touch detection electrode TDL associated with thereference data DR (a reference touch detection electrode) will bedescribed.

FIGS. 11A and 11B each schematically illustrate an example of anoperation of the reference touch detection electrode. FIG. 11Aillustrates an example where the external proximity object is located ona lower side of the touch detection plane. FIG. 11B illustrates anexample where the external proximity object is located on an upper sideof the touch detection plane.

For example, when the external proximity object is located on the lowerside of the touch detection plane as illustrated in FIG. 11A, the touchdetection signal Vdet of a touch detection electrode TDLT correspondingto a position of the external proximity object contains many touchcomponents, whereas the touch detection signal Vdet of an uppermosttouch detection electrode TDLR contains few touch components and theexternal noise component is dominant. In other words, the touchdetection data DT associated with the touch detection electrode TDLTbecomes the smallest, and the touch detection data DT associated withthe touch detection electrode TDLR becomes the largest. The maximumvalue selecting circuit 45 selects the touch detection data DT belongingto the touch detection electrode TDLR as the reference data DR. Hence,in this example, the uppermost touch detection electrode TDLR serves asthe reference touch detection electrode.

Similarly, in an example where the external proximity object is locatedon the upper side of the touch detection plane as illustrated in FIG.11B, the touch detection signal Vdet of the touch detection electrodeTDLT corresponding to a position of the external proximity objectcontains many touch components, whereas the touch detection signal Vdetof a lowermost touch detection electrode TDLR contains few touchcomponents and the external noise component is dominant. In other words,the touch detection data DT associated with the touch detectionelectrode TDLT becomes the smallest, and the touch detection data DTassociated with the touch detection electrode TDLR becomes the largest.The maximum value selecting circuit 45 selects the touch detection dataDT belonging to the touch detection electrode TDLR as the reference dataDR. Hence, in this example, the lowermost touch detection electrode TDLRserves as the reference touch detection electrode.

Then, the subtracting section 47 subtracts the reference data DR fromthe touch detection data DT (Step S3). More specifically, the memory 46sequentially outputs the accumulated touch detection data DT of the onedetection frame, and the subtracting section 47 subtracts the referencedata DR from each of the outputted touch detection data DT. In otherwords, the reference data DR corresponding to the external noisecomponent is subtracted from each of the touch detection data DTcontaining both the touch component and the external noise component, tothereby extract the touch component.

Then, the coordinate extracting circuit 49 extracts the touch coordinatein the touch detection plane (Step S4). More specifically, thebinarizing circuit 48 first performs the binarization by comparing therespective data outputted from the subtracting section 47 with thethreshold values. The coordinate extracting circuit 49 then obtains,based on the data outputted from the binarizing circuit 48, the touchcoordinate in the touch detection plane of the touch detection functiondisplay unit 10. Thereby, the coordinate at which the touch or theproximity is made or occurred is obtained based on the data in which theexternal noise component is reduced.

This ends a flow of the operation in the touch detection circuit 40. Theflow described above is performed separately for each detection frame.

A prototype of the display device having the touch detection function 1described above was fabricated to measure a signal-to-noise (S/R) ratiothereof. The measurement of the S/R ratio was conducted in a state inwhich a finger as the external proximity object was located at aposition separated at a predetermined distance from a part near thecenter of the touch detection region. The S/R ratio was 1.4 when thesubtracting process of deducting the reference data from the touchdetection data DT was performed, whereas the S/R ratio was 1.1 when nosubtracting process was performed. Hence, it was confirmed that theperforming of the subtracting process improves the S/N ratio.

Effects

According to the first embodiment, the reference data is acquired fromone of the plurality of touch detection electrodes. Hence, an electrodeused for a detection of the external noise is eliminated, making itpossible to simplify the configuration of the touch detection unit 30.Also, what is desired in deducting the external noise component issimply to subtract the reference data DR from the touch detection dataDT. Hence, it is possible to make the configuration of the touchdetection circuit 40 simple.

Also, according to the embodiment, the touch detection electrode forobtaining the reference data is selected from the plurality of touchdetection electrodes. Hence, it is possible to reduce the external noisecomponent in a precise fashion irrespective of a location of theexternal proximity object.

Further, according to the embodiment, the average value calculatingsection obtains the average values of the touch detection data DT of therespective touch detection electrodes, and the touch detection electrodefor obtaining the reference data is selected based on the obtainedaverage values. Hence, even when the touch detection data DT includes anaccidental or sporadic noise, an influence of such a noise is kept tothe minimum by the averaging, making it possible to further ensure thatthe touch detection electrode for obtaining the reference data isselected.

First Modification

In the embodiment described above, the maximum value selecting circuit45 that selects the maximum value of the data supplied from the averagevalue calculating section 44 is used, although it is not limitedthereto. As one embodiment, it is preferable that a minimum valueselecting circuit be used in place of the maximum value selectingcircuit 45, when the polarity of the touch detection signal Vdetinputted to the touch detection circuit 40 has a characteristic reverseto that of the embodiment described above (i.e., the touch detectionsignal Vdet is low in voltage when there is no touch or proximity, andhigh in voltage when there is touch or proximity), or when the LPFsection 41 has a function of inverting an input voltage, for example.FIG. 12 illustrates an example of a circuit configuration of a touchdetection circuit 40A that performs the touch detection based on thetouch detection signal Vdet having the reversed polarity. A minimumvalue selecting circuit 45A is an arithmetic circuit that selects, foreach one detection frame, the minimum one of the data supplied from theaverage value calculating section 44, and outputs the selected minimumdata as the reference data DR. The reference data DR in thismodification likewise corresponds to the external noise component, andthe touch component is extractable by subtracting the reference data DRfrom the touch detection data DT in the subtracting section 47.

Second Modification

In the embodiment described above, the average value calculating section44 obtains the average data DAVG for each of the touch detectionelectrodes TDL, and the touch detection electrode TDL for obtaining thereference data DR is selected based on the obtained average data DAVG,although it is not limited thereto. As an alternative embodiment, amaximum value calculating section 44B may obtain a maximum value of thetouch detection data (a maximum data DMAX) of each of the touchdetection electrodes TDL, and may select the touch detection electrodeTDL for obtaining the reference data DR based on the obtained maximumdata DMAX, as illustrated in FIG. 13, for example. In other words, themaximum value calculating section 44B obtains a minimum of a magnitude(or an absolute value) of a sum of the touch component and the noisecomponent in a detection signal for each of the touch detectionelectrodes TDL, and selects one of those minimum values in which themagnitude of the sum of the touch component and the noise component isthe smallest. That is, a minimum of the absolute value of the sum of thetouch component and the noise component, both contained in the detectionsignal outputted from the corresponding detection electrode, isdetermined for each of the detection electrodes, a smallest minimum isselected from the plurality of minimums obtained, and a detection signalwhich has brought the smallest minimum is used as the reference. Themaximum value calculating section 44B and the maximum value selectingcircuit 45 in this modification are likewise capable of extracting theexternal noise component. As in the first modification described above,it is preferable that the maximum value selecting circuit 45 be changedto the minimum value selecting circuit and the maximum value calculatingsection 44B be changed to a minimum value calculating section in FIG.13, when the polarity of the touch detection signal Vdet is reversed,for example.

3. SECOND EMBODIMENT

A display device having a touch detection function according to a secondembodiment will now be described. The display device having the touchdetection function according to the second embodiment has aconfiguration similar to that described in the first embodiment(illustrated in FIGS. 4, 8, etc.), except that a touch detection circuitdoes not employ the memory that accumulates the touch detection data DTof the one detection frame.

FIG. 14 illustrates an example of a circuit configuration of a touchdetection circuit 50 according to the second embodiment. The touchdetection circuit 50 according to this embodiment has a configuration inwhich the memory 46 is omitted as compared with the touch detectioncircuit 40 (FIG. 8) according to the first embodiment described above.

In one embodiment, the LPF section 41, the ADC section 42, the digitalLPF section 43, the average value calculating section 44, the maximumvalue selecting circuit 45, and the subtracting section 47 are aspecific example of a “signal correction section”.

FIG. 15 is a flowchart of an operation of the touch detection circuit50. The touch detection circuit 50, when the touch detection signalsVdet each containing the touch component and the external noisecomponent are inputted in accordance with the scanning of one detectionframe, extracts, as the reference data DR, the external noise componentfrom the touch detection data DT that correspond to the touch detectionsignals Vdet. Then, in accordance with the scanning in a subsequent onedetection frame, the touch detection circuit 50 subtracts the referencedata DR, extracted in the preceding one detection frame, from each ofthe touch detection data DT belonging to that subsequent one detectionframe, to thereby obtain the touch component. Then, the touch detectioncircuit 50 extracts, based on the obtained touch component, thecoordinate at which the touch or the proximity is made or occurred inthe touch detection plane. In the following, description is given oneach step.

First, the touch detection circuit 50, in accordance with the scanningof the one detection frame, calculates the average value of the touchdetection data DT for each of the touch detection electrodes TDL (StepS11). More specifically, the LPF section 41, the ADC section 42, and thedigital LPF section 43 generate, based on the touch detection signalsVdet inputted from the touch detection electrodes TDL, the touchdetection data DT. Then, the average value calculating section 44calculates the average value of the touch detection data DT in onedetection frame period TF of each of the touch detection electrodes TDL,and outputs the respective thus-calculated average values as the averagedata DAVG.

Then, the maximum value selecting circuit 45 selects, as the referencedata DR, the maximum one of the average values among the touch detectiondata DT that are obtained by the average value calculating section 44for the respective touch detection electrodes TDL (Step S12). This stepS12 is similar to the step S2 described above.

Then, the subtracting section 47 subtracts, in accordance with thescanning of the subsequent one detection frame, the reference data DRthat is obtained in the preceding one detection frame from each of thetouch detection data DT (Step S13). More specifically, the subtractingsection 47 subtracts the reference data DR from each of the touchdetection data DT. Herein, since the memory employed in the firstembodiment described above is omitted in this embodiment, the touchdetection data DT are supplied to the subtracting section 47 inaccordance with the scanning of the one detection frame. The referencedata DR, on the other hand, is obtained based on the touch detectiondata DT that belong to the preceding detection frame.

Then, the coordinate extracting circuit 49 extracts the touch coordinatein the touch detection plane (Step S14). This step S14 is similar to thestep S4 described above. This ends a flow of the operation in the touchdetection circuit 50.

According to the second embodiment described above, the memory thataccumulates the touch detection data DT of one detection frame iseliminated. Hence, it is possible to allow the circuit configuration ofthe touch detection circuit to be simple, and to reduce the time ittakes to detect the touch or the proximity. Other effects achieved bythe second embodiment are similar to those according to the firstembodiment.

Third Modification

As one embodiment, the configuration of the second embodiment describedabove may be modified by employing the minimum value selecting circuitin place of the maximum value selecting circuit 45 when, for example,the polarity of the touch detection signal Vdet is reversed, as in thefirst embodiment.

Fourth Modification

As one embodiment, the configuration of the second embodiment describedabove may be modified by employing the maximum value calculating section44B in place of the average value calculating section 44, as in thefirst embodiment. The maximum value calculating section 44B and themaximum value selecting circuit 45 in this modification are likewisecapable of extracting the external noise component.

4. APPLICATION EXAMPLES

Application examples of the display devices having the touch detectionfunction according to the embodiments and the modifications will now bedescribed with reference to FIGS. 16 to 20G. Each of the display deviceshaving the touch detection function according to the embodiments and themodifications is applicable to any electronic unit in any field. Theelectronic unit may be, for example but not limited to, a televisiondevice, a digital camera, a computer including a desk-top personalcomputer and a laptop personal computer, a portable terminal deviceincluding a cellular phone, a video camera, or any other suitabledevices. In other words, the display devices having the touch detectionfunction according to the embodiments and the modifications areapplicable to electronic units in all of fields, which display, as animage or a video image, a video signal inputted from the outside orgenerated internally.

First Application Example

FIG. 16 illustrates an external appearance of a television device towhich the display device having the touch detection function accordingto any one of the embodiments and the modifications described above isapplied. The television device is provided with an image display screenunit 510 including a front panel 511 and a filter glass 512, forexample. The image display screen unit 510 includes the display devicehaving the touch detection function according to any one of theembodiments and the modifications described above.

Second Application Example

FIGS. 17A and 17B each illustrate an external appearance of a digitalcamera to which the display device having the touch detection functionaccording to any one of the embodiments and the modifications describedabove is applied. The digital camera is provided with a light emittingunit 521 for flash, a display unit 522, a menu switch section 523, and ashutter-release button 524, for example. The display unit 522 includesthe display device having the touch detection function according to anyone of the embodiments and the modifications described above.

Third Application Example

FIG. 18 illustrates an external appearance of laptop personal computerto which the display device having the touch detection functionaccording to any one of the embodiments and the modifications describedabove is applied. The laptop personal computer is provided with a body531, a keyboard 532 for input-manipulation of characters and the like,and a display unit 533 for displaying an image, for example. The displayunit 533 includes the display device having the touch detection functionaccording to any one of the embodiments and the modifications describedabove.

Fourth Application Example

FIG. 19 illustrates an external appearance of a video camera to whichthe display device having the touch detection function according to anyone of the embodiments and the modifications described above is applied.The video camera is provided with a body 541, a lens 542 provided in afront face of the body 541 for picking-up an image of an object, ashooting start/stop switch 543, and a display unit 544, for example. Thedisplay unit 544 includes the display device having the touch detectionfunction according to any one of the embodiments and the modificationsdescribed above.

Fifth Application Example

FIGS. 20A to 20G each illustrate an external appearance of a cellularphone to which the display device having the touch detection functionaccording to any one of the embodiments and the modifications describedabove is applied. The cellular phone couples an upper casing 710 and alower casing 720 through a coupling part (or a hinge) 730, and isprovided with a display 740, a sub-display 750, a picture light 760, anda camera 770, for example. The display 740 or the sub-display 750includes the display device having the touch detection functionaccording to any one of the embodiments and the modifications describedabove.

Although the application has been described in the foregoing by way ofexample with reference to the embodiments, the modifications, and theapplication examples to the electronic units, the application is notlimited thereto but may be modified in a wide variety of ways.

For example, in the embodiments described above, the average valuecalculating section obtains the average values of the touch detectiondata DT (i.e., obtains the average data DAVG), and the maximum valueselecting circuit selects the maximum value from those average data DAVGto generate the reference data DR, although it is not limited thereto.In an alternative embodiment, the average value calculating section mayperform the addition only, and the maximum value selecting circuit mayperform the division after selecting the maximum value to generate thereference data DR, for example.

Also, as one embodiment, the subtracting section 47 may subtract thereference data DR from the touch detection data DT when the externalproximity object is away from the touch detection plane (i.e., aproximal state), and may output the touch detection data DT directly oras they are when the external proximity object touches the touchdetection plane (i.e., a contact state). This allows it to operate toreduce the external noise only when the external proximity object is inthe proximity state in a case where, for example, the external noisebecomes problematic in the proximity state.

Also, in the embodiments described above, the drive electrodes COML aresequentially scanned by selecting those drive electrodes COML one byone, although it is not limited thereto. In an alternative embodiment,the plurality of drive electrodes COML may be selected at a time toperform the sequential scanning thereof.

Also, in the embodiments described above, the dot-inversion drive, inwhich the polarity of the pixel signal is inverted for each dot, isemployed as a display drive scheme of the liquid crystal display unit,although it is not limited thereto. In an alternative embodiment, thedisplay drive scheme may be a so-called line inversion drive in whichthe polarities of the pixel signals are inverted for each line, or maybe a so-called frame inversion drive in which the polarities of thepixel signals are inverted for each frame.

Also, in the embodiments described above, the display drive signal isthe direct current signal having the voltage of zero volts, although itis not limited thereto. In an alternative embodiment, the display drivesignal may be the direct current signal having other voltage, or may bean alternating current signal. In the embodiment where the display drivesignal is the alternating current signal, the liquid crystal displayunit is driven based on a so-called alternating current drive.

Also, in the embodiments described above, the display period B isprovided after the touch detection period A in one display horizontalperiod (1H), although it is not limited thereto. In an alternativeembodiment, the touch detection period A may be provided after thedisplay period B in one display horizontal period (1H).

Also, in the embodiments described above, the touch detection functiondisplay unit 10 has the configuration in which the liquid crystaldisplay device 20 including the liquid crystal in any of the variousmodes such as the TN mode, the VA mode, and the ECB mode and the touchdetection unit 30 are integrated. In an alternative embodiment, theliquid crystal display unit including the liquid crystal in a transverseelectric mode such as a FFS (Fringe Field Switching) mode and an IPS(In-Plane Switching) mode and the touch detection unit may beintegrated. In the embodiment where the liquid crystal in the transverseelectric mode is employed, a touch detection function display unit 60may be configured as illustrated in FIG. 21. FIG. 21 illustrates anexample of a cross-sectional configuration in a major part of the touchdetection function display unit 60. Referring to FIG. 21, a liquidcrystal layer 6B is sandwiched between a pixel substrate 2B and anopposed substrate 3B. Since names, functions, etc. of other elements arethe same as those in the embodiment described with reference to FIG. 5,those elements will not be described in detail. Unlike the embodiment ofFIG. 5, the drive electrodes COML in this embodiment, which are sharedfor both the displaying and the touch detection, are formed immediatelyabove the TFT substrate 21, and structure a part of the pixel substrate2B. The pixel electrodes 22 are arranged above the drive electrodes COMLwith an insulating layer 23 in between. In this embodiment, all ofdielectrics, including the liquid crystal layer 6B as well, between thedrive electrodes COML and the touch detection electrodes TDL contributeto the formation of the electrostatic capacitance C1.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope and without diminishing itsintended advantages. It is therefore intended that such changes andmodifications be covered by the appended claims.

The application is claimed as follows:
 1. A display device having atouch detection function, the display device comprising: a displaysection performing display based on an image signal; a plurality ofdrive electrodes arranged side-by-side and extending in a direction; aplurality of detection electrodes arranged side-by-side, extending tointersect the drive electrodes, allowing an electrostatic capacitance tobe formed at each of intersections of the drive electrodes and thedetection electrodes, and each outputting a detection signal in responseto driving of each of the drive electrodes; a signal correction sectioncorrecting the detection signals outputted from the detectionelectrodes, through determining a reference based on the detectionsignals, and through subtracting the determined reference from each ofthe detection signals; and a detecting section detecting an externalproximity object based on corrected detection signals provided from thesignal correction section, wherein the drive electrodes function as aplurality of display horizontal lines for the display section by beingsupplied with a display drive signal, and function as a plurality ofdetection horizontal lines for detecting the external proximity objectby being supplied with a touch detection signal for generating thedetection signal, and touch detection is performed in each predeterminedperiod, and a touch detection period in which the touch detection isperformed by being supplied with the touch drive signal and a displayperiod in which display is performed by being supplied with the displaydrive signal are not overlapped with each other, wherein thepredetermined period is shorter than one frame period that includes aplurality of touch detection periods and a plurality of display periods,and the display is performed by using one drive electrode in eachdisplay period, and the touch detection is performed by using one driveelectrode in each touch detection period, wherein the touch detectionperiod and the display period are alternately repeated in the one frameperiod such that scanning of the touch detection is performed throughoutan entire touch detection plane, and wherein the signal correctionsection corrects the detection signals based on the detection signalsobtained in the one frame period.
 2. The display device having a touchdetection function according to claim 1, further comprising a driveelectrode driver supplying the display drive signal and the touchdrive-signal to the drive electrodes, wherein the drive electrode driversequentially selects one of the drive electrodes as a target beingsupplied with the touch drive signal when detecting the externalproximity object by the plurality of detection horizontal lines.
 3. Thedisplay device having a touch detection function according to claim 1,wherein the signal correction section calculates, for each of thedetection electrodes, a time-average of absolute value of a sum of atouch component and a noise component both contained in the detectionsignal outputted from the corresponding detection electrode, selects asmallest time-average from the plurality of time-averages obtained, anduses, as the reference, a time-average of a detection signal which hasbrought the selected smallest time-average.
 4. The display device havinga touch detection function according to claim 1, wherein the signalcorrection section determines, for each of the detection electrodes, aminimum of absolute value of a sum of a touch component and a noisecomponent both contained in the detection signal outputted from thecorresponding detection electrode, selects a smallest minimum from theplurality of minimums obtained, and uses, as the reference, a detectionsignal which has brought the smallest minimum.
 5. The display devicehaving a touch detection function according to claim 1, wherein thesignal correction section subtracts the current reference from each ofthe current detection signals, the current reference being determinedfrom the current detection frame, the current detection signals beingobtained from the respective detection electrodes in the currentdetection frame.
 6. The display device having a touch detection functionaccording to claim 5, wherein the signal correction section temporarilyholds the current detection signals obtained from the respectivedetection electrodes.
 7. The display device having a touch detectionfunction according to claim 1, wherein the signal correction sectionsubtracts the preceding reference from each of the current detectionsignals, the preceding reference being determined from the precedingdetection frame, the current detection signals being obtained from therespective detection electrodes in the current detection frame.
 8. Thedisplay device having a touch detection function according to claim 1,wherein in the touch detection period, the respective drive electrodesare sequentially supplied with the touch detection signal, and when anyone of the drive electrodes is supplied with the touch drive signal, theother drive electrodes are not supplied with the touch drive signal andthe display drive signal.
 9. The display device having a touch detectionfunction according to claim 1, wherein a touch detection by onedetection horizontal line using one drive electrode, and a display bypixels corresponding to one display horizontal line using the one driveelectrode that is used as the one detection horizontal line areperformed for each of the drive electrodes sequentially.
 10. The displaydevice having a touch detection function according to claim 1, whereinthe predetermined period corresponds to a horizontal period.